The Continental Drift Controversy: Evolution into Plate Tectonics
By using a dynamical approach of core-magma angular momentum exchange, this study theoretically explains the continental formation and plate drift as well as main mountain uplifts in the early Earth period. The present mantle and lithosphere were the partial part of magma fluid layer (mantle currents) before and after the Earth's crust formation. Thus, a theory is presented regarding the driving forces of plate drift, in the form of planetary scale mantle currents. The origin of mantle currents is traced back to the formation of the solar system. It is assumed that small particles (nebula matter) orbiting the Sun assembled, and a molten sphere of primordial Earth with different minerals evenly distributed throughout the total mass came into existence. Subsequently , a process called planetary differentiation took place, as the core and mantle currents (magma layer) started separating. This will inevitably cause the Earth to spin faster, and it is presumed that the inner core first gained angular velocity, thereby spinning faster than the material found at a shallower depth. The time interval of the angular momentum exchange between the core and the magma should have lasted for at least 0.1-0.2 billion years. Planetary scale vertical and horizontal circulations of mantle currents took place, and angular momentum exchange was realized through the vertical component. The horizontal part of the mantle currents, near the bottom of the lithosphere, became a real force to drive continental split and plate drift. The acceleration and deceleration of the core compared with the mantle currents then caused different flow directions in the two hemispheres. When the inner core rotates faster from west to east, upper mantle currents will tend to flow westwards and towards the two poles. Surface lighter materials converged towards the two poles so that two continental polar crust caps appeared when the magma surface was cooling. This caused two original su
Using digital educational resources (DERs) in science education is an effective way of promoting students' content knowledge of complex natural processes. This work presents the usage of the digital educational resource CreativeLab_Sci&Math | Plate Tectonics, designed for exploring the PhET™ Plate Tectonics simulator, in the context of the education of pre-service teachers (PSTs) in Portugal. The performance of the PSTs was analysed based on the five tasks into which the DER was organized. Results show that the DER contributed to the successful achievement of the following learning outcomes for PSTs: describing the differences between the oceanic crust and continental crust regarding temperature, density, composition and thickness, associating the plate tectonic movements with their geological consequences, and identifying the plate tectonic movements that cause the formation of some geological structures. Results also show that PSTs considered the PhET™ Plate Tectonics simulator a contributor to their learning about plate tectonics.
Textbooks teach the principles of science. Lyellʼs geology textbooks emphasized vertical crustal movement. He avoided far-fetched continental-drift hypotheses by Hopkins in 1844 and Pepper in 1861. Their notions of drift were supported by fossil and paleoclimate evidence, but their causes were global magnetism and electrochemical crystallization and dissolution. Danaʼs textbooks from 1863 to 1895 taught that the symmetry of North America proved it had always stood alone; thus Americans were conditioned to reject Wegenerʼs concept of a Carboniferous supercontinent. Unaware of Wegenerʼs hypothesis in 1912, Schuchert launched a textbook series that guided American geological opinion from 1915 to the 1960s. His paleogeographic models required Carboniferous land bridges to connect fixed continents. He and coauthors Longwell and Dunbar eventually realized that Wegenerʼs continental-drift hypothesis would disprove land-bridge theory and solve problems of mountain ranges, paleoclimates, and fossil distributions, but they guarded against it in their textbooks. Already in 1927, Holmes proposed that convection with sea-floor spreading drove continental drift, but editor Schuchert would not publish that breakthrough. Geologists Du Toit, Van der Gracht, Holmes, Shand, Bailey, and Grabau showed the merits of continental drift, but their publications had little impact. Willis accepted the invitations of Schuchert in 1932 and Longwell in 1944 to write papers opposing Wegenerʼs hypothesis. Simpson contributed with paleontologic opposition. In 1944 Holmes published a British textbook that showed how continental drift could change geology. It was Holmes, Carey, and Wilson, as much as the Americans Hess and Dietz, who should be credited with instigating the plate-tectonic revolution.
This chapter discusses the work of the Earthquake Junkies over the last several decades. Taking the opposite view to that of Mike Davis, and his famous essay “The Case for Letting Malibu Burn” (Davis, Ecology of fear: Los Angeles and the imagination of disasters, Vintage Books, New York, 1998), the chapter describes how experts and scientists in the Bay Area have joined forces to—they hope—save San Francisco from a large-scale earthquake. This chapter focuses on the anthropology exploration of the expert’s definition of earthquakes as an object of science, its translation into public policy and scientific experimentation. We will explore how the improvement of mitigation projects lie in the articulation of different existences of earthquakes. Finally, we will see how decades of work have addressed earthquake risk in the Bay Area and have, despite sometimes mixed results, laid the foundation for solid risk awareness for all residents in this seismically volatile region.
It is now more than fifty years since Tuzo Wilson published his paper asking “Did the Atlantic close and then re-open?”. This led to the “Wilson cycle” concept in which the repeated opening and closing of ocean basins along old orogenic belts is a key process in the assembly and breakup of supercontinents. This implied that the processes of rifting and mountain building somehow pre-conditioned and weakened the lithosphere in these regions making them susceptible to strain localization during future deformation episodes. Here we provide a retrospective look at the development of the concept, how it was evolved over the past five decades, current thinking and future focus areas. The Wilson Cycle has proved enormously important to the theory and practice of geology and underlies much of what we know about the geological evolution of the Earth and its lithosphere. The concept will no doubt continue to be developed as we gain more understanding of the physical processes that control mantle convection, plate tectonics, and as more data become available from currently less accessible regions.
The continental drift controversy has been deeply analysed in terms of rationalist notions, which seem to find there a unique topic to describe the weight of evidence for reaching consensus. In that sense, many authors suggest that Alfred Wegener’s theory of the original supercontinent Pangea and the subsequent continental displacements finally reached a consensus when irrefutable evidence became available. Therefore, rationalist approaches suggest that evidence can be enough by itself to close scientific controversies. In this article I analyse continental drift debates from a different perspective which is based on styles of thought. I’ll argue that continental drift debate took much longer than it was usually recognized with two styles of thought coexisting for hundreds of years. These were fixism and mobilism and they were always confronting their own evidence and interpretations and functioning as general frameworks for the acceptability of a specific theory. Therefore, this text aims to bring much broader sociological elements than usually involved in the analysis of the continental drift theory.
In the 1960s the once discarded theory of continental drift proposed by Alfred Lothar Wegener was substantially revised and transformed into the modern standard theory of global plate tectonics. For a decade or so the new theory of the Earth and the traditional contraction theory faced competition from a third alternative, the hypothesis of the expanding Earth. As early as 1952 Jordan had suggested Earth expansion on the basis of decreasing gravity, and a few years later the suggestion was taken up by several physicists and earth scientists. Dicke seriously applied his skills in fundamental physics to a broad range of geophysical problems, including a possible increase in the Earth’s radius. The Hungarian geophysicist László Egyed was not only a leading figure in the expansionist alternative but also an advocate of varying gravity as the cause of the growing Earth. Other geologists and geophysicists in favour of the expanding Earth preferred to present their chosen theory in purely empirical terms, without considering the cause of the expansion.
Large-scale lateral mobility of the Earth’s lithosphere (mobilism) was a hotly debated issue in Earth Sciences during some two decades following publication of Wegener’s (1912) theory of continental displacement. The final acceptance of lithospheric mobility was brought about with the plate tectonics revolution during the late 1960s. Support for mobilism was rather popular in certain European countries during the 1920s, whereas the reactions in North America were mostly hostile. One of the very few influential mobilists in the New World was Reginald Aldworth Daly of Harvard University. The present paper discusses his model of continental displacement which is very remarkable in many aspects. We focus on the hitherto neglected fact that Daly proposed in the mid-1920s a mechanism to create oceanic crust which would have been totally consistent with the Vine–Matthews hypothesis of seafloor generation published in 1963. It is furthermore suggested that Daly’s geotectonic proposals were inspired by small-scale analogues of lava flows and multiple dike swarms he observed on Atlantic islands such as St. Helena and Ascension. His model to account for the construction of new oceanic crust is reminiscent of the models of Vine and Moores (1972) and Cann (1970) which eventually led to the “Penrose-definition” of ophiolites in 1972. As these scientists arrived at their conclusions absolutely independently of Daly, this episode is an instructive example of a multiple or repeated discovery in the Earth Sciences which renders it difficult to believe certain theories of science which assume scientific models to depend mostly on social factors.
John Tuzo Wilson (1908–1993) was one of the greatest Canadian scientists of the 20th century. His contributions to Earth Sciences, leading the formulation of the theory of plate tectonics, have revolutionized our understanding of how the planet Earth works and evolved over the past 4 billion years. This 50th anniversary special issue of the Canadian Journal of Earth Sciences is dedicated in honour of John Tuzo Wilson, who inspired tens of thousands of students all around the world to study the Earth. This special issue contains 12 papers dealing with various aspects of the “Wilson Cycle” in the geologic record, plate tectonics, mantle plumes, and how John Tuzo Wilson accepted “continental drift” and formulated the theory of plate tectonics. The contributions have mostly been made by geoscientists who directly or indirectly associated with John Tuzo Wilson and have contributed significantly to the plate tectonics paradigm.
Tuzo Wilson’s well-known pre-1961 opposition to continental drift stemmed from his early experience as a geologist in the Appalachians and the Canadian Shield, which convinced him that orogenesis did not change drastically over geologic time. Conversely, Taylor (in 1910) and Wegener (in 1912) hypothesized that continental drift began in Cenozoic or Mesozoic time. Between 1949 and 1960, Tuzo Wilson with Adrian Scheidegger developed a quasi-uniformitarian model of progressive continental accretion around fixed Archean nuclei. Tuzo abruptly jettisoned this model in 1961 when, under pressure from paleomagnetic evidence for continental drift and a nascent concept of sea-floor spreading, he finally entertained the possibility of pre-Mesozoic as well as younger continental drift. He immediately found it a superior fit to Appalachian and Shield geology, while his uniformitarian conviction remained intact. Tuzo had blinded himself to the evidence for continental drift so long as he confined it to Taylor or Wegener’s conception. In continental drift operating continuously over geologic time, he found a theory he could eagerly accept.
ResearchGate has not been able to resolve any references for this publication.